Assuming the relic calls Grimm or that you might want to use it again hiding it in the strongest kingdom seems reasonable to me, rather than just digging a random hole in the ground. I really like the efficiency the show moved through plot when it didn’t want to concentrate on something.

It is a good thing we only have a vague idea what is happening next. For all we know they’ll end up stowing away on the same ship as Cinder and Neo.